1. Field of the Invention
The present invenion pertains to apparatus for machining pipe or the like. More specifically, the present invention pertains to portable apparatus suitable for field machining of pipe, e.g., threading, rethreading, facing, refacing, etc.
2. Description of the Prior Art
Sections of pipe are frequently connected for various purposes. These pipe sections may be connected in several ways. Many are connected by a threaded joint in which external threads at the end of one section of pipe threadedly engage internal threads of another section of pipe. In drilling for oil and gas, such threaded pipe joints are used to join sections of drill pipe which extend from drilling rig down to the drilling bit.
The seal between the adjacent drill string pipe sections is usually provided by metal to metal engagement of a shoulder on the male or pin end of a pipe and the annular end face of the female or box end of the adjacent pipe. It is important that this seal be maintained. Due to the hostile environment and rough handling of drill pipe, the seal faces and the pipe threads are frequently damaged in the field. In the past, the damaged pipe sections were sent to a machine shop for refacing and/or rethreading. Since the pipe must necessarily be transported from the field to the machine shop and back to the field, this process is quite costly.
In recent years, portable machines have been developed for refacing of damaged pipe joints. Examples of such portable refacing machines may be seen in U.S. Pat. Nos. 3,124,024; 3,181,398; 3,691,882; 3,717,055; 4,130,034 and 4,149,436. Most of these machines utilize some type of support or mandrel which is attached to the pipe to be machined by engagement with the threads thereof. Some type of cutting tool is then provided which, upon proper rotation and feeding, cuts a new surface or face on the pipe joint.
Thus, a pipe joint can be refaced in the field at a much less cost than transporting the pipe to a machine shop for repair thereof. Such refacing machines are therefore useful if the pipe joint requires refacing only. However, if the threads are damaged or if it is necessary to cut off a portion of the pipe and cut new threads and faces thereon, such portable facing machines are not adequate. In particular, there does not appear to be a portable machine capable of field rethreading a damaged joint or capable of cutting new threads on a joint which has been cut off.